I am not sure what is causing this. I drilled a 3mm pilot hole for my unibit (which starts at 4) but the unibit doesn't get much further than half a millimetre in before it catches and jumps out. I am not using a drill press, I am doing it by hand. I was told that the drill bit was suitable for aluminium but I am now worrying that it is too soft seeing as another bit manged to make 5 successful holes in the same enclosure. Am I right? What might be causing this?